(1) Field of the Invention
The invention relates to a process for manipulating workpieces, which are to be carburized. In this process the workpieces or workpiece magazines that are to be deposited on a pallet are loaded in several rows, corresponding to a predefined number of rows of workpieces, into a rotating hearth furnace. Then after carburization they are removed from the rotating hearth furnace and fed to a hardening press, exhibiting a predetermined number of press stations, and on each pallet are deposited a number of workpieces or workpiece magazines, the number corresponding to the number of press stations.
(2) Description of the Related Art
During the thermal treatment of the workpieces as mass production parts for case hardening, different types of furnaces are used as a function of the quantity and size of the workpieces. Small or thin-walled workpieces, such as synchronous rings or gearshift sleeves for motor vehicle gear shifts, can be heated in a rotating hearth furnace in a relatively short period of time and processed to a sufficient hardness penetration depth ranging from approximately 0.2 to 0.3 mm. For complete utilization of the furnace chamber and to obtain many hours of carburization, the workpieces to be carburized are usually positioned on single pallets in multilayered grate systems. They are put with the loaded xe2x80x9cgreen partsxe2x80x9d, that is workpiece blanks that have not been carburized yet, into the rotating hearth furnace. After carburization, they are removed from the furnace and fed to a hardening press, exhibiting a predetermined number of press stations. The number of workpieces, to be deposited on each pallet, is defined by the number of press stations (press station number) in the hardening press.
In designing a workpiece hardening system, comprising essentially a rotating hearth furnace and a hardening press, it is important that the capacity of both the furnace and the press is utilized in such a manner that there are no idle times. To this end, the pallets are arranged in a circular row in the rotating hearth furnace. At one charging site of the rotating hearth furnace, a pallet or workpiece magazines with already carburized workpieces is/are removed, and the rotating hearth furnace is loaded with a pallet of green compacts.
It is known from German utility model 269 08 569 to load a pallet, instead of with individual workpieces, with one or several workpiece magazines, where several workpieces are stacked in each workpiece magazine.
The invention is based on the problem of designing the aforementioned manipulation in such a manner that the capacity of both the rotating hearth furnace and the hardening press can be better utilized. To this end the invention provides that the pallets in the rotating hearth furnace are arranged in such a number of rows that the number of workpiece rows is a multiple of the number of press stations. The invention makes it possible to couple, for example, smaller hardening presses with few press stations with larger rotating hearth furnaces, in which a larger number of workpiece rows can be accommodated, because there is no longer any need to maintain the same number of press stations as the number of workpiece rows. Thus, smaller hardening presses can be coupled with larger rotating hearth furnaces as a function of the respective carburization time without incurring any idle times.
Special embodiments of the invention are disclosed in the dependent claims.
In the following the invention is explained in detail with reference to the attached drawings.